It is estimated that over 90% of oysters, clams, and mussels produced for consumption worldwide come from aquaculture farms. In particular, due to loss of wild oyster reefs, small-scale aquaculture of oysters has increased significantly in recent years. Typical shellfish aquaculture farms utilize baskets, cages, trays, racks, or similar containers for holding the oysters either on the water bottom or off-bottom. The oysters and aquaculture equipment remain submerged in natural water bodies for extended periods of time during the growth of the oyster to a matured state suitable for harvest. During submerged periods, a biofilm of microorganisms may form on outer surfaces of the shellfish and the submerged aquaculture equipment, which can lead to the attachment of nuisance bio-fouling organisms such as barnacles and unwanted bivalve shellfish. Bio-fouling organisms create nuisance by clogging mesh or pores in shellfish containers, which reduces water flow through the containers and food availability for the shellfish, thereby slowing growth of culture shellfish. Additionally, bio-fouling organisms attach directly to shellfish causing visual defects that reduce market value. Unwanted organisms also add excessive weight to the system and can damage moving parts of the aquaculture equipment. Periodic emergence of the equipment and shellfish in the air above the sea surface for about 24 hours desiccates the biofilm before it sufficiently establishes to permit attachment of bio-fouling organisms. Emergence of the equipment eliminates the need to pressure wash or clean equipment and shellfish by other means after bio-fouling organisms colonize the exposed surfaces.
In productive shellfish growing areas such as the Gulf of Mexico, desiccation of gear at weekly intervals is typically required to control bio-fouling. Currently employed methods for bio-fouling control rely on intensive and potentially unsafe manual labor practices. Typical aquaculture systems comprise rectangular containers constructed of heavy plastic coated wire mesh that are assembled with multiple container compartments for holding flexible plastic mesh bags of varying mesh sizes that contain shellfish at various growth stages. The containers typically have two air-filled floats attached to the top of the containers on the outside edges on opposing sides to maximize stability to wave action. The air-filled floats provide adequate buoyancy to float the oyster-filled containers below the surface of the water for growing the oysters. The normal bio-fouling practice employed with floating aquaculture systems is to manually flip the containers upside down so the floats are on the bottom of the containers. Float buoyancy elevates the oysters and the containers in the air above the water surface. In shallow areas, flipping the containers is often done by wading, but boats are required to work deeper or colder waters. Relatively calm waters are required to flip the containers from boats. After a desiccation period of about 24 hours, the containers are manually flipped back into the growth position until the next desiccation treatment. This method of bio-fouling control is labor intensive and time consuming, which drives up oyster production costs. In addition, there are safety risks involved with the manual flipping of the oyster-filled containers, which can be extremely heavy. To limit the weight, smaller containers or groups of containers must be utilized, thereby limiting the potential scale of an operation.
Accordingly, a need exists in the art for a shellfish aquaculture apparatus and method that allows for simple, fast, and safe bio-fouling control.